1. Field of the Invention
The present invention relates to a bearing system for a vertical type rotary machine including a vertically extending rotor shaft.
2. Description of the Prior Art
A bearing system of the aforementioned type of the prior art includes an oil tank, disposed around the rotor shaft and containing lubricating oil, and a guide bearing disposed around the rotor shaft in concentric relation thereto for guiding the rotor shaft. The guide bearing includes upper and lower end surfaces and a cylindrical bearing surface extending therebetween and juxtaposed against the periphery of the rotor shaft. The bearing surface has a lower peripheral portion thereof dipped in the lubricating oil in the oil tank. A plurality of axially extending oil grooves are formed in the cylindrical bearing surface. Each of the oil grooves has opposite other axial ends thereof opening into the upper and lower end surfaces, respectively, of the guide bearing, a bottom surface, leading and trailing side surfaces with respect to the direction of rotation of the rotor shaft.
The oil grooves each have associated therewith one oil guide member which is secured to the lower end surface of the guide bearing adjacent to the trailing side surface of the associated oil groove. Each of the oil guide members is provided with a guide surface facing the flow of lubricating oil in the oil tank induced by the rotation of the rotor shaft for introducing the lubricating oil into the associated oil groove. The guide surface extends in a plane including the axis of the rotor shaft and is coextensive with the trailing side surface of the oil groove, and has the same radial width as the trailing side surface of the oil groove.
With the arrangement, when the flow of lubricating oil in the above noted oil tank induced by the rotation of the rotary shaft impinges against the guide surface of each oil guide member, the majority of the lubricating oil escapes around a lower edge and a radially outward edge of the guide surface, and the volume of the lubricating oil introduced into the oil groove is very small thereby decreasing the lubricating and cooling functions by the oil.
When the rotor shaft rotates, the lubricating oil in the oil tank would be agitated to engulf air into the oil so that fine air bubbles are formed in the oil. As the flow of the oil, induced by the rotation of the rotor shaft, impinges against the guide surface of each oil guide member and stagnates at the guide surface, the air bubbles entrained by the oil flow are collected at the stagnating point and are joined to each other so that the fine bubbles grow into large air bubbles. The large air bubbles move upwardly in the oil groove and cause discontinuity in an oil film formed between the rotor shaft and the guide bearing, thereby causing seizure to occur.